A method of manufacturing a branched pipe whereby a pipe blank is partially swelled by pressurizing the inner surface of the pipe blank has been widely known. According to such a manufacturing method, a swelled part can be swelled from a main body of the pipe blank.
Now, methods of simultaneously recessing and swelling a tip portion of the swelled part have been proposed for uniformly forming the thickness of the swelled part (see Japan Laid-open Patent Application Publication Nos. JP-A-2000-117341 and JP-A-S55-144334).